1. Field of the Invention
The present invention relates generally to a wind dam device used to reduce the air drag of tractor-trailers. In particular, the invention relates to an inflatable wind dam for reducing the air drag of a moving tractor-trailer located on the back or leeward side of the trailer. The wind dam is cone-shaped and comprised of two longitudinally opposed sections, each section having an outer shell and an inner inflatable bladder contained therein. The wind dam has an inflatable mating joint for maintaining the form and structure of the opposed sections of the cone-shaped wind dam.
2. Background
Various devices are currently known to increase the aerodynamic efficiency of a truck, semi trailer, or other large moving object. It has long been recognized that the rectangular high profile shape of these vehicles and the speeds necessary for travel increase the amount of air drag, which can account for about half of the fuel consumption in trucking. While the remaining fuel waste is due to the amount of weight carried in the vehicle as well as the engine efficiency, reducing the effects of air drag has the greatest potential to reduce overall fuel consumption and is one of the easier factors to manipulate.
The devices currently known to increase aerodynamic efficiency, while somewhat effective, suffer from a number of drawbacks. The previous devices have been attached to the back of trucks often include loose pieces that must be attached and removed to accommodate loading and unloading. As a result, the pieces are easy to lose, and are time consuming to assemble because they are heavy and bulky making them difficult to both attach and remove. Similarly, other devices do not allow for the convenient loading and unloading of the trailer""s cargo because they consist of a single attached unit that must be removed in order to open and close the trailer doors. Furthermore, often the prior art devices are ineffective in that they provide little drag reduction when in use or are costly to produce and install.
For these reasons inflatable drag resistors have become preferred because they are light, inexpensive, and may be collapsed without the use of an excessive number of moving parts, examples of such devices are disclosed in U.S. Pat. No. 4,978,162 (Labbe), U.S. Pat No. 5,236,347 (Andrus), U.S. Pat. No. 5,375,903 (Lechner) and U.S. Pat. No. 5,832,610 (Ryan et al.). However, despite the preference of inflatable wind dams, not many are in use because they still tend to fail in solving the problems currently associated with wind dams, for instance, there is the continued difficultly created when loading and unloading the tractor-trailer because the wind dam is attached as one unit to the back. (See Lechner, Andrus). Similarly, Ryan et al. uses a single attached unit in which the unit is rolled in and out of a container for storage. Thus Ryan et al. teaches a complicated system again utilizing numerous moving parts, which is difficult to use and maintain.
To allow for easy loading and unloading of the tractor-trailer it is necessary to develop a system formed of two halves that combine to form a whole unit when inflated. Thus, providing for air drag reduction while still permitting easy loading and unloading of the trailer. Labbe discloses a system that solves this problem by separating the unit, creating two halves to function together as a single wind dam. However, Labbe""s system fails to connect the adjacent halves in a way that prevents them from interfering with each other during operation. Furthermore, Labbe""s wind dam inflates through the movement of the truck instead of through the use of a control device and is not protected when un-inflated, both of which create a situation that leaves the wind dam vulnerable to damage.
Accordingly a need exists for an improved wind dam device for effectively reducing the air drag of a tractor-trailer.
An object of the present invention is to provide a wind dam device for effectively reducing the air drag of a tractor-trailer.
The present invention intends to overcome the difficulties encountered heretofore. To that end, the invention comprises an inflatable cone-shaped wind dam for reducing the air drag of a moving tractor-trailer. The wind dam is comprised of two longitudinally opposed sections each section having an outer shell and an inner inflatable bladder, constructed so that the outer shell houses the inner inflatable bladder. The cone-shaped wind dam further comprises an inflatable mating joint for maintaining the form and structure of the wind dam.